Meat contamination occurs when it contains harmful substances or microorganisms, like bacteria or parasites, that can cause illness. As a source of foodborne diseases worldwide, these products represent a public health concern. The presence of these contaminants can spoil food or lead to infections when consumed.
Pathways of Contamination
The journey of meat from farm to fork is complex, with multiple points where contamination can occur. This pathway begins at the production level, where animals can be exposed to pathogens through their feed, water, or environment. Healthy animals can carry microbes in their intestines that, while harmless to them, can be transferred to meat during later stages.
The slaughtering and processing phase is a frequent point for contamination. During slaughter, pathogens from an animal’s hide or intestinal contents can be transferred to the sterile muscle tissue. Cross-contamination is also an issue in processing facilities, where bacteria can spread from unclean equipment, surfaces, or the hands of workers.
Contamination can also happen during distribution and retail. If meat is not kept at the proper temperature during transportation, bacteria can multiply. Improper handling at the grocery store or butcher shop, such as using the same tools for different meats without cleaning them, can also spread harmful microbes.
Common Contaminants and Associated Illnesses
A variety of contaminants can be found in meat, but biological pathogens are the most common cause of foodborne illness. These include bacteria, parasites, and viruses. Each type of pathogen can be associated with specific meats and cause distinct illnesses with a range of symptoms.
Bacteria are a primary concern in meat safety. Salmonella is frequently found in the intestines of birds and mammals and can contaminate raw poultry, pork, and beef. Ingesting Salmonella leads to salmonellosis, an infection with symptoms like diarrhea, fever, and stomach cramps that appear 6 hours to 6 days after exposure. Campylobacter is another bacterium linked to raw or undercooked poultry and is a leading cause of bacterial foodborne illness. The resulting illness, campylobacteriosis, causes symptoms like bloody diarrhea, fever, and cramps within two to five days of consumption.
Certain strains of Escherichia coli, particularly O157:H7, are another concern, often found in undercooked ground beef. This pathogen can cause severe abdominal cramps, bloody diarrhea, and vomiting. In young children and older adults, an E. coli O157:H7 infection can lead to a life-threatening complication called hemolytic uremic syndrome (HUS), which causes kidney failure. Listeria monocytogenes can be found in processed meats, including deli meats and hot dogs, and causes listeriosis, which is especially dangerous for pregnant women and those with weakened immune systems.
Parasites in meat are less common but still pose a risk. Trichinella is a roundworm whose larvae can be present in the muscle tissue of animals, notably pigs and wild game. If meat containing these larvae is eaten raw or undercooked, it can cause trichinosis. Initial symptoms may include nausea and diarrhea, followed weeks later by muscle pain, fever, and swelling around the eyes.
Beyond biological pathogens, meat can also be subject to chemical and physical contamination. Chemical contaminants can include residues from cleaning agents or veterinary drugs. Physical contaminants are foreign objects that accidentally end up in meat, such as pieces of metal from machinery, plastic, or bone fragments.
Identifying and Handling Potentially Contaminated Meat
Consumers often rely on their senses to determine if meat is safe, but this method has limitations. Spoilage bacteria can cause noticeable changes, such as a sour or foul off-odor. The texture of the meat might also become sticky or slimy, and discoloration, like poultry turning grey or red meat becoming brown, can also be a sign of spoilage.
However, many of the most dangerous pathogens, including Salmonella, E. coli, and Listeria, do not produce any detectable changes in the smell, appearance, or taste of meat. A piece of meat can be heavily contaminated and still seem perfectly fresh. For this reason, you should never taste meat to check if it is safe.
The most reliable approach is to be cautious. If you have any reason to suspect that meat might be spoiled or contaminated—due to its smell, texture, or appearance—it is best to discard it. The guiding principle is simple: when in doubt, throw it out.
Safe Meat Handling and Prevention in the Home
Preventing foodborne illness from meat at home relies on fundamental food safety practices. These can be broken down into four main areas: cleaning, separating, cooking, and chilling. Adhering to these steps can significantly reduce the risk of infection.
First, maintaining cleanliness is foundational. This involves washing your hands with soap and warm water for at least 20 seconds before and after handling raw meat. Also, wash all surfaces, cutting boards, and utensils that contact raw meat in hot, soapy water to prevent the spread of bacteria.
Separating raw meat from other foods is an important step to avoid cross-contamination. Use a separate cutting board for raw meat, poultry, and seafood than the one you use for ready-to-eat foods like vegetables. In your refrigerator, store raw meat in sealed containers on the bottom shelf to prevent its juices from dripping onto other foods.
Cooking meat to the correct internal temperature is the most effective way to kill harmful bacteria. Since color is not a reliable indicator of doneness, using a food thermometer is the only way to be sure. Ground meats like beef and pork should be cooked to 160°F (71°C), all poultry should reach 165°F (74°C), and whole cuts like steaks and roasts should be cooked to at least 145°F (63°C).
Properly chilling meat is the final piece of the safety puzzle. Perishable foods, including raw and cooked meat, should be refrigerated promptly, within two hours of purchasing or cooking. Your refrigerator should be set to 40°F (4°C) or below to slow bacterial growth. Store leftovers in shallow containers to cool quickly and use them within three to four days.